Max Planck Institute for Dynamics and Self-Organization -- Department for Nonlinear Dynamics and Network Dynamics Group
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Arbeitsgruppen-Seminar

Tuesday, 05.05.2015 17 c.t.

Ballistic transport in graphene antidot lattices

by Dr. Jonathan Eroms
from Institut für Experimentelle und Angewandte Physik, Universität Regensburg

Contact person: Theo Geisel

Location

Ludwig Prandtl lecture hall

Abstract

By embedding graphene in a hexagonal boron nitride (hBN)/graphene heterostructure, the sample quality, electron mobility and carrier homogeneity can be drastically enhanced. In particular, using a dry stacking technique, any contact of the graphene layer to process chemicals such as photoresist is avoided, resulting in consistently high sample qualities. Nanopatterning of those samples can be an additional source of sample degradation, and therefore has to be assessed in a suitable experiment. Here we use electron beam lithography and reactive ion etching of the entire hBN/graphene/hBN stack to prepare antidot arrays with lattice periods of down to 100 nm. Magnetoresistance measurements on those samples at low temperatures show pronounced peaks corresponding to ballistic electron orbits around one or several antidots, which proves the high carrier mobility even after the nanopatterning step. We also observe phase-coherent effects, namely Aharonov-Bohm oscillations and weak localization, where the phase coherence length greatly exceeds the lattice period, again showing that the high sample quality is preserved. Finally, in a sample with a combination of a moiré lattice and an antidot lattice, the interplay of those different modulations is studied.

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